Single channel and multi-channel iontophoretic devices are known in the prior art. Turning to FIG. 1, a single channel iontophoretic controller 110 is illustrated connected in-vivo (i.e., connected to a human arm 112). Regulated current flows from the controller to the active electrode 114. The inactive electrode 116, in this example, is not utilized for drug delivery. Instead, it is used solely to provide a return path for the electrical current.
As illustrated in FIG. 1, the controller 110 includes a DC/DC converter that is used to convert the voltage from the power source to a higher voltage. A typical power source is a 9 Volt alkaline battery (e.g., MN1604).
A typical general-purpose commercial iontophoretic controller (e.g., IOMED PM700) includes a DC/DC converter that converts the finite battery voltage to a magnitude ranging from approximately 0.0 Volt to 70.0 Volts. The value within this range is dependent on skin resistance and current. The DC/DC converter is optional, for example some low voltage application-specific commercial iontophoretic controllers do not require, and therefore do not employ a DC/DC converter. Therefore, as used herein, the term “current regulator” shall mean either a current regulator working in conjunction with a DC/DC converter or working in conjunction with a different type of power supply that does not employ a DC/DC converter (e.g., a simple unregulated battery source power supply).
In FIG. 1, the microcontroller interfaces bi-directionally with the current regulator. In other words the microcontroller controls and monitors the current regulator. The feedback (i.e., the monitoring) is required to regulate the current if the closed-loop regulation is partly or fully controlled by the microcontroller. It is also required to verify the correct operation of the current regulator. Parameters that are measured include current and voltage. From these basic parameters additional parameters can be calculated. For example the IOMED PM700 Phoresor, which was manufactured and distributed by IOMED from 1990 to 1997. Although this device is no longer manufactured, the description provided herein also applies to PM700 successors (i.e., PM800 and PM850) and related devices (e.g., PM900). The circuitry of the PM700 measures iontophoretic current and iontophoretic output voltage. From these two basic parameters at least two additional parameters are calculated: di/dt (i.e., the rate of change of the current with respect to time) and iontophoretic dose (i.e., the integral of current with respect to time, i.e., milliAmp-minutes, i.e., charge). The monitoring of voltage, current, and the rate of change in current, is desired from both a functional and safety standpoint.
Dose is monitored as required to either display the dose (e.g., on a LCD) and/or to terminate the treatment after a finite magnitude of dose (charge) is accumulated. Voltage is monitored to verify that the iontophoretic resistance is within limits. If the resistance is too high for a given iontophoretic current setting, then the PM700 alerts the user via a “Resistance Limit” warning. If the rate of change of the current is too excessive, then the PM700 disables the iontophoretic current and issues an “Electrode Reject” error. If the measured current (i.e., “feedback”) significantly deviates from the desired current (i.e., from the “command signal”), then the PM7000 disables the iontophoretic current and issues an “Electrode Reject” error.
Turning to FIG. 2, a single channel iontophoretic controller 210 is connected to two active electrodes 214A, 214B via a bifurcated cable assembly. The controller in this illustration is an lontorhor-PM. This is a commercial iontophoretic controller than has been manufactured and sold in the United States for several years. The lontophor-PM bifurcated cable assembly has also been manufactured and sold for several years.
The feature of utilizing a bifurcated cable assembly to provide two channels of current from a single channel device is not limited to the lontophoretic-PM, and therefore will work with any single channel iontophoretic controller (note the equivalence of the PM700 block transformation in FIG. 1 and the block transformation of the lontophor-PM in FIG. 2).
The bifurcated cable assembly supposedly provides approximately equal current to two body sites, thereby facilitating non-isolated multi-channel operation. However, due to differences in skin-body resistance, the two currents can deviate significantly. In addition, the two currents cannot be individually monitored. For example, if the first active electrode is improperly placed on the body, or if it is defective, or if the cable connection to this electrode is defective, then all of the current will flow through the second active electrode. As such, a bifurcated cable assembly cannot be used in any application that mandates regulated currents. More specifically the bifurcated cable assembly may be unacceptable from a functional and safely standpoint depending on the application.
Turning to FIG. 3, a block transformation of an EMPI DUPEL iontophoretic controller 310 connected in-vivo is provided wherein U.S. Pat. Nos. 5,189,307, 5,254,081, 5,283,441 and 5,431,625 are related thereto in addition to the instructions for use of the EMPI DUPEL iontophoretic controller. Part No. 360165, © 1991, 1992. Empi, Inc. In FIG. 3, the dual channel iontophoretic controller 310 is connected to two isolated pairs of electrodes. Current “I1” is isolated and totally independent from Current “I2”. Because the two channels are electrically isolated, operation is analogous to utilizing two single channel iontophoretic controllers.
Turning to FIG. 4, a simplified block transformation is depicted of a device described by U.S. Pat. No. 5,310,403. As described, this iontophoretic drug delivery device 410 employs multiple open-loop current sinks and/or multiple open-loop current sources. Because the sinks, or alternatively, the sources are operated in an open-loop mode, there is no current regulation. In other words, current “I1” may deviate from current “I2.” Deviation may be a result of component variation, component degradation, component failure, ambient conditions (e.g., temperature), etc. Additionally, if there is a defect in electrode construction, or in the cable assembly, the associated iontophoretic current will be incorrect or totally absent for that particular channel. Likewise, if the user incorrectly hydrates an electrode, or incorrectly adheres an electrode, or the like, then the current will be incorrect or totally absent for that particular channel. The faults that have just been described will unfortunately be tolerated by the iontophoretic device because the current in each channel are not monitored, i.e., there is no closed-loop regulation from an electronic control statepoint, and additionally there is no feedback monitoring for functionality or safety. Further, the currents in each channel cannot be independently controlled.
It is the purpose of this invention to provide a solution to many, if at not all, of the above stated problems.